Black box pings raise hopes of finding missing airplane

Muslim men offer a special prayer for passengers aboard the missing Malaysia Airlines Flight MH370 after a Friday prayer at National Mosque in Kuala LumpurThe towed pinger locator (TPL-25) sits on the deck of the Australian Defence Vessel Ocean Shield in the southern Indian OceanJapan's Maritime Self-Defence Force Commander Hidetsugu Iwamasa is pictured in front of one of their P-3C Orion aircraft currently at RAAF Base Pearce near Perth on April 4.On Monday it will be 30 days since the Malaysia Airlines flight MH370 lost communications and disappeared from civilian radar less than an hour into an overnight flight from Kuala Lumpur to BeijingMalaysia's Defence Minister and acting Transport Minister Hishammuddin Hussein speaks at a news conference at the Putra World Trade Centre (PWTC) in Kuala Lumpur on April 5.

The hunt for the missing Malaysia Airlines plane entered a new phase yesterday when a Chinese ship reported hearing possible signals from a black box flight recorder.

On day 29 of the search for Flight MH370, a series of 'pings' from the depths of the Indian Ocean appeared to constitute the first solid lead.

A Chinese survey vessel, Haixun 01, heard a pulse with a frequency of 37.5kHz per second – identical to the standard signal used by the locator beacon of a flight recorder.

The ship was scanning the seabed west of Australia and north of the main search area. A reporter with the Chinese state broadcaster who was on board Haixun, said the ship had first picked up the signal on Friday, when pings were detected intermittently for about 15 minutes. At the time, other vessels were in the vicinity, raising the possibility that they were the source.

Haixun then heard the signal again yesterday, when the pings were picked up every second for 90 seconds. Xinhua, the official Chinese news agency, cautioned that there was still no confirmation of any link with the missing Malaysian passenger jet. Haixun had reported hearing the "pulse signal" and was conducting further investigations, added Xinhua.

Last night, Air Chief Marshal Angus Houston, a retired Australian officer co-ordinating the search effort, said the signals had not been verified but added: "I have been advised that a series of sounds has been detected by a Chinese ship in the search area. The characteristics reported are consistent with the aircraft black box."

The sea in this area of the Indian Ocean is nearly 4,500 metres deep – almost 5km – and is criss-crossed by submerged mountain ranges, with peaks rising 2,500 metres from the seabed.

Black boxes can be detected at a maximum range of about 3,000 metres, suggesting that if the signals were genuine, then Haixun must be relatively close to the target. Objects floating in the sea, which may have been wreckage, were also photographed by a Chinese reconnaissance aircraft 100km from where Haixun detected the pings.

Haixun is a patrol and survey ship operated by the China Coast Guard. Weighing 5,400 tons and with a length of 430ft, the vessel is capable of conducting search, rescue and survey missions thousands of miles from their naval base.

Beacons attached to flight recorders send out a 'ping' every second for about 30 days. The frequency is chosen to distinguish the signal from the background 'noise' of the ocean. Ten military aircraft and 11 vessels are now taking part in the hunt for MH370.